The present invention relates to an apparatus for monitoring the movement and force production of the lumbar spine during flexion and extension of the trunk of a patient in each of several sagittal-frontal planes of the body, and during trunk twisting. The apparatus is useful in the design of ergonomically suitable workplaces, and in the analysis and rehabilitation of low back disorders.
Occupationally related low back disorders have become a problem of epidemic proportion in the industrialized world in recent years, and has been recognized as a major problem in the industrial environment. It is widely known that the majority of low back disorders associated with the workplace involve muscular over-exertion injuries. These injuries occur frequently and are quite acute initially but may progress to a more chronic state with repetitive strains. One of the basic concepts in the ergonomic control of the workplace is to design manual materials handling tasks so that the strength required by the task does not exceed most workers capabilities.
Worker strength has traditionally been evaluated using isometric strength tests of workers in the sagittal plane, i.e. the extension/flexion plane. The machines which are currently marketed for measuring movement in the sagittal plane are of limited utility, however, since they can not assess motion components that are commonly found in the workplace or everyday life, and which are asymmetric. Machines of this general type are illustrated, for example, in Smidt et al, U.S. Pat. No. 4,462,252 and Boethcher, U.S. Pat. No. 4,565,368. Also, a similar machine is sold by Cybex, a division of Lumex, Inc. of Bay Shore, N.Y., and as described in U.S. Pat. No. 4,725,054 to Solow et al.
Machines are also available for assessing movement in the transverse (i.e. twisting) plane, and a machine of this general type is manufactured by Cybex, as the Cybex TR unit. Note also the Skowronski U.S. Pat. No. 4,732,381. Here again, however, these machines are of limited utility in that they are unable to assess commonly encountered motions which include components in addition to twisting.
Isotechnologies Inc., of Hillsboro, N.C., currently markets a low back testing and rehabilitation machine under the designation Iso Station.RTM. B-200, which includes a fixed platform upon which the patient stands, and a stabilizing belt system for locking the legs in a fixed upright position while the patient stands on the platform. The upper body is attached to a harness arrangement, which permits the upper body to move in three planes while the legs are fixed, namely the flexion/extension plane, the transverse (twisting) plane, and the lateral flexion plane. The apparatus also permits bending outside of the sagittal plane during flexion/extension movement. The movements in each of these planes are monitored, with the apparatus operated either dynamically or isometrically. This apparatus is also described in U.S. Pat. No. 4,768,779 to Oehman et al.
While the above described Iso Station.RTM. machine is better able to assess complex motion as compared to the above described single function machines, it does not permit the assessment of the lumbar movement of the spine in any specifically selected plane or combination of planes, since there is no control of the path of movement of the upper trunk. Thus there is an inherent inability to interpret the results accurately with respect to workplace determined demands, since patients produce different motions.
U.S. Pat. No. 5,094,249 to Marras et al discloses an apparatus for monitoring movement of the lumbar spine during flexion and extension, as well as during twisting. Also, the apparatus includes a platform upon which the patient stands and which is rotatable about a vertical axis, and so that the platform may be moved to and locked in a selected angular orientation, and the apparatus may then be operated in either a flexion/extension mode, or a twisting mode.
While the apparatus as described in the above patent to Marras represents a significant advance in the art in that it may be selectively configured to monitor the motion components during bending in the flexion/extension plane, or during movement in the transverse plane, and while assuming a symmetric or asymmetric trunk position, further improvement is deemed desirable in that the mass of the patient supporting framework is relatively large, which renders it difficult for the patient to easily start and stop the movements.
It is accordingly an object of the present invention to provide an apparatus which may be selectively configured to monitor the motion components during flexion/extension movement, or during twisting, and which has a moveable framework of reduced mass so as to provide easier control of the movements.
It is also an object of the present invention to provide an apparatus of the described type, and which is capable of operation in either mode while the patient assumes a symmetric or asymmetric trunk position.